The adult liver retains the capacity to grow to meet altered functional demand and for compensatory regeneration of lost or damaged tissue. An early intracellular hepatic change during the onset of the growth process is a large increase in the nuclear content of polyamines covalently conjugated to protein. What the protein substrates are and their role in cell function is unknown. The aim of this project is to determine what role the conjugation of polyamines to liver protein plays in the hepatic growth process. This will be accomplished by a combined biochemical and immunochemical approach. The putative nuclear conjugating enzyme will be purified; its identity as a transglutaminase determined; its physical nd kinetic features established; its similarity to the cytoplasmic enzyme tested; and an antibody developed to the purified protein and utilized to study expression of the enzyme in different hepatic states. The ability of specific phospholipids to support enzyme activity at physiological CA++ concentrations will be determined. The proteins to which the polyamines are conjugated will be purified and their physical and chemical characteristics determined. Co-identity of the conjugates with known nuclear proteins will be explored using two-dimensional electrophoresis. Antibodies to the purified polyamine-protein conjugates will be raised and utilized to study the intracellular regulation of the conjugated and unconjugated proteins during changing hepatic states. The effect of the addition of the purified conjugates on nuclear RNA synthesis, and the relevance of conjugation to that effect, will be tested. The post-translational modification of proteins by the covalent attachment of a butylamine or propylamine group could have conformational and/or functional consequences similar tothose established for protein phosphorylation. The accomplishment of these studies should yield new information regarding the mechanisms by which nuclear events are regulated in the hepatic cell during the growth process.